1. Field of the Invention
This invention relates to the mixing of fluid components and is directed more particularly to a liner for use with mixing containers, and an assembly and method for mixing fluid components in a liner-equipped mixing container.
2. Description of the Prior Art
The mixing of paint in facilities wherein paint is used on a large scale, as, for example, in automotive production plants, often is conducted in metal drums, e.g., common 55 gallon drums, equipped with a short upstanding post fixed to the center of the interior bottom surface.
Referring to FIG. 1, it will be seen that a typical prior art mixing assembly includes a 55 gallon cylindrical container 10 having a closed end wall 12 and an open end 14. A post 16 is affixed to and upstands about 21/4 inches, or so, from the interior surface 18 of the closed end wall 12.
The assembly further includes a mixing shaft 20 to which there are fixed mixing elements, such as blades 22. Mixing shaft 20 is hollow, or else it has a cavity 24 at its bottom end so as to permit the mixing shaft to be rotatably mounted on post 16. The shaft 20 extends through a central opening 26 in a cover member 28.
In operation, a fluid, typically comprising two or more paint components, is introduced into the container 10 to a suitable level. The mixing shaft 20, with cover member 28 thereon, is then placed in the container 10. The bottom end 24 of the shaft 20 is positioned so that post 16 is received by the shaft bottom end. Cover member 28 is secured to the top of the container 10 to close the otherwise open end 14 thereof. This results in the shaft 20 being generally aligned with the longitudinal axis of container 10. The blades 22 are rigid and extend close to, and are spaced from, the interior surface of side wall 15 of container 10.
The top end 32 of the mixing shaft 20 is then engaged by an electrically-powered turning device (not shown) which turns the shaft 20, thereby moving the blades 22 through the fluid. Alternatively, the upper end of the shaft can be coupled to a manually-operated turning mechanism (also not shown).
Upon completion of the mixing operation, cover member 28 and mixing shaft 20 with blades 22 are removed from the container 10. The mixed paint is then transferred to other containers or used directly from the container 10. In either case, the container 10 is not suitable for further like use and hence must be discarded. Disposal of the 55 gallon metal containers is objectionable because (1) the modified 55 gallon drums are expensive (typically costing more than $20 per drum) and (2) the drums are relatively large and disposing of thousands of drums involves a large disposal volume.
In an effort to render the mixing containers reusable, there has been provided a liner 40 (FIG. 2) for use with the mixing container 10 (FIG. 3). The liner 40 comprises a sleeve 42 closed off by a bottom end wall 44 thereof and having an open top end 46. Liner 40 is of a configuration generally complementary to the interior configuration of container 10. Sleeve 42 is of a flexible fluid-impervious material, preferably polyethylene or another flexible fluid-impervious plastic material.
A fitment 50 is fixed to an interior surface 48 of the bottom end wall 44 of the sleeve 42 and is open at a bottom end 52 (FIG. 2) thereof, and closed at a top end thereof. The fitment 50 is of an elongated configuration generally complementary to the configuration of the post 16. The bottom end wall 44 of the sleeve 42 defines a hole 56 (FIG. 2) in alignment with the fitment open bottom end 52. The fitment 50 may be provided with a flange portion 58 by which the fitment 50 is affixed to the interior surface 48 of the sleeve bottom end 44, as by adhesive, ultra-sonic welding, heat sealing, or other bonding process.
Fitment 50 preferably is of a plastic material or a high density elastomer. The fitment 50 is relatively stiff so as to resist twisting in response to rotation of shaft 20.
In operation, the liner 40 is inserted into the container 10, with the fitment 50 fitting over and receiving post 16 through the hole 56 and open bottom end 52 of the fitment 50. The fluid (e.g. paint components) is then poured into the open end of liner 40, causing the liner 40 to be pressed against the side and bottom end walls 15, 12 of the container 10. The mixing shaft 20 is inserted into the container 10 over the fitment 50 and post 16. The cover 28 is pressed down over the open end 46 of sleeve 42 and a complementary rim 49 of container 10 to lock the cover 28 to the upper end 14 of the container 10, to close the assembly (FIG. 3). The mixing shaft 20 is then rotated by a rotative apparatus engaged with the shaft top end 32.
Upon completion of the mixing operation, cover 28 and mixing shaft 20 are removed from the container 10, and the mixed paint (or other fluid) is removed form the container. Upon emptying the container, the liner 40 is stripped from the container, the interior of which has been protected by the removed liner from contact with the fluid.
The liner may be made with a relatively small wall thickness. Since it also is flexible, the liner 40 may be folded into a relatively small volume of space for disposal purposes, while the container may be re-used. The cost of liner 40 is much less than the cost of the container 10, and the space required for disposal of the liner 40 is very much less than the space required for disposal of the container 10.
The above-described liner and associated assembly and method is shown and described in U.S. Pat. No. 5,727,878, issued Mar. 17, 1998 to Joseph J. Sullivan, Jr. While the liner has successfully rendered mixing drums, even paint mixing drums, reusable, providing for the post 16 contributes substantially to the cost of the drum and, once done, limits the market for the drum to essentially purchasers having need for mixing containers. That is, the expense added to the manufacture of the drum tends to remove the drum from the general market and confine sales of the drum to a specialty niche. From the perspective of the users of mixing drums, the drums with posts mounted therein are substantially more expensive than the standard drum.
There is thus a need for a mixing assembly wherein the mixing container is an ordinary unmodified drum, and the cost of a mixing enabler is less expensive.